Articulated frame steer tractor



Aug. 20, 1968 K. SALNA 3,397,752

ARTICULATED FRAME STEER TRACTOR Original Filed Dec. 23, 1964 2Sheets-Sheet 1 51 .52 Lgg 37 i0 20 25 11 INVENTOR.

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Aug. 20, 1968 s N 3,397,752

ARTICULATED FRAME STEER TRACTOR Original Filed Dec. 23, 1964 2Sheets-Sheet 2 E F'W INVENTOR.

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United States Patent 3,397,752 ARTICULATED FRANIE STEER TRACTOR KarlSalna, Mundelein, .lll., assignor to International Harvester Company, acorporation of Delaware Continuation of application Ser. No. 420,683,Dec. 23, 1964. This application July 15, 1966, Ser. No. 565,655

1 Claim. (Cl. 180-51) This invention relates in general to vehicles, andmore particularly to articulated vehicles of the frame-steer type.

It is a well-known expedient to articulate front and rear sections of avehicle and steer the vehicle by mechanically varying the angularrelationship between the sections. The concept is widely utilized inheavy construction vehicles and, more specifically, in vehicles designedfor earth moving and highway construction.

A large articulated rubber tire'bulldozer, for example, usually includesa front section supported for travel on a wheel truck and mounting abulldozer blade. The front section is connected for pivotal movementabout a generally vertical axis to a rear section which is alsosupported on a wheel truck. Hydraulic motor means interconnect thesections and effect angular movement between them to induce steeringunder the control of an operator. Such articulated steering isespecially advantageous in construction vehicles because of the greatversatility of maneuverability it affords.

With heavy earth moving equipment particularly, however, the effects ofarticulation are not all meritorious. As the angular relationshipbetween vehicle sections becomes more acute, for example, greater sideloading is thrown onto the front wheels by the driving effect of therear wheels. This side loading has a tendency to lift the inside frontwheel slightly off the terrain and, consequently, tireslippage occurs.In a four-wheel drive vehicle, such tire slippage results in unequaland, consequently, damaging load factors and loss in performance beingeffective on the vehicle.

It is an object of the present invention to provide an improvedarticulated vehicle construction.

It is another object to provide an improved articulated vehicleconstruction which automatically compensates for side-loading on thefront Wheels of the vehicle as it works in articulated relationship.

It is still another object to provide an improved articulated vehicleconstruction wherein a predetermined amount of side-loading compensationis built into the vehicle, depending upon the average load factoranticipated.

It is yet another object to provide an articulated material handlingvehicle such as a bulldozer or the like wherein tire slippage due toside loading during working in articulated relationship is substantiallyeliminated.

It is a further object to provide an articulated vehicle constructionwhich has a built-in self-straightening effect for road travel and thelike.

It is still a further object to provide an articulated vehicle having anew and improved wheel truck mounting.

It is yet a further. object to provide an articulated vehicle includinga pivot mounting arrangement for the rear wheel truck meansincorporating a bearing arrangement which minimizes bearing. wear.

The foregoing and other objects are realized in accord with the presentinvention by providing a canted axis articulated vehicle. The normallyvertical pivot axis between vehicle sections is inclined rearwardly apredetermined number of degrees. Accordingly, when the vehiclearticulates to turn, the front section tilts slightly about itslongitudinal axis toward the inside of the turn. The amount of inwardtilt is pre-calculated to compensate for outward tilt of the frontsection induced by the couple defined between the driving force of therear wheels 3,397,752 Patented Aug. 20, 1968 ice acting along thelongitudinal axis of the rear vehicle section and the reactive force ofthe terrain acting on the front wheels at ground level. Accordingly,front wheel slippage is substantially avoided.

A further aspect of the invention resides in the relationship betweenthe rear vehicle section and its supporting wheel truck. The rearvehicle section is mounted on its wheel truck for pivotal movementrelative thereto about the longitudinal axis of the section, whereby therear wheel truck is able to closely follow the often rough terrain. Thepivotal mounting arrangement for the truck includes a universal jointarrangement which substantially eliminates thrust bearing play in thetruck mounting.

The invention, both as to its organization and method of operation,taken with further objects and advantages thereof, will best beunderstood by reference to the following description taken in connectionwith the accompanying drawings, in which:

FIGURE 1 is a side elevational view of an articulated bulldozerembodying features of the present invention;

FIGURE 2 is a diagrammatic plan view of the wheel arrangement of thevehicle illustrated in FIGURE 1, during straight and articulated travel;

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 2, with thevehicle in articulated travel;

FIGURE 4 is a diagrammatic plan view of a conventional articulatedbulldozer subjected to normal loading While working in articulatedrelationship;

FIGURE 5 is a sectional view taken along line 55 of FIGURE 4; and

FIGURE 6 is a bottom plan view of the rear vehicle section in thearticulated vehicle illustrated in FIGURE 1.

Referring now to the drawings, and particularly to FIGURE 1, anarticulated four-wheel drive material handling vehicle embodyingfeatures of the present invention is illustrated generally at 10. Thevehicle 10 includes a rear vehicle section 11 connected for articulatedmovement about an axis 12 to a front vehicle section 13. A conventionalbulldozer blade assembly 15 is mounted on the front vehicle section 13.

According to the present invention the axis 12 of articulation isinclined rearwardly. The rearward inclination of the axis 12 causes thefront vehicle section 13 to tend to lean slightly toward the inside of aturn as the vehicle 10 works in articulated relationship. The extent towhich the front section 13 leans toward the inside of a turn as thevehicle 10 works in articulated relationship is determined by the angleof rearward inclination of the axis 12 and is designed to be sufiicientto precisely balance any tendency of the front vehicle section 13 totilt toward the outside of the turn under the influence of side loadingon the front vehicle section. The front vehicle section loses tractionif it tilts toward the outside while working in a turn, of course. In afour-wheel vehicle 10 such loss of traction on one side results inunequal loading on the vehicle and other detrimental side effects.

The forces which are elfectively balanced by the rearward inclination ofthe axis 12 in the vehicle 10 according to the present invention areillustrated in FIGURES 4 and 5. FIGURE 4, for example, diagrammaticallyillustrates a conventional articulated vehicle in plan view at V. In theworking relationship illustrated, the vehicle V is articulated at aboutits conventional vertical pivot P as the bulldozer blade B engages aload.

Working in this articulated relationship, the reardriving wheels RW ofthe vehicle V exert a force indicated by the arrow at the pivot P alongan axis perpendicular to the planes of the front driving wheel FW. Theeffect of this force acting perpendicularly to the front driving wheelFW in a conventional articulated bulldozer is to introduce a tippingmoment in the front Wheels FW equal to the force exerted by the drivingrear wheels RW 3 times the radius r of the front wheels FW, asillustrated in FIGURE 5. The reactive force of the front wheels FWgripping the terrain creates a couple which tends to tilt the frontsection of the vehicle V.

If the inner of the front Wheels FW lifts off the ground, slippageoccurs and unequal loading is effected on the vehicle V, of course.Where the front wheels FW are driving wheels, lifting of an inside frontwheel FW slightly off the ground causes the blade B to tilt which cuts ahole and the operator could not hold a grade or level cut.

According to the present invention, the tendency of the inside frontwheel FW on the vehicle V illustrated in FIGURES 4 and 5 to lift olT theterrain is counteracted by canting the pivot axis P of the vehiclerearwardly. The angular inclination of the axis P is determined by theload factors or range of load factors with which the bulldozer V willwork. The load factors to be considered include the horsepower rating ofthe vehicle and the load capacity of the blade B, and especially if theblade B is replaced with front end loader where the load is carried highand the dynamic stability is of most importance. With the vehicleworking in articulated relationship, a force component F exerted by therear wheels RW is directed toward the blade B. correspondingly, thereactive force component P of the load acting on the front wheels FW iscanted at an angle to the bulldozer blade B in the direction of travelof the rear wheels RW. Thus, it will be seen that greater forcecomponents F beget greater reactive force components F and a greatertendency of the front wheels FW to tilt outwardly is effected.

Turning now to the details of construction of the vehicle constructedaccording to the present invention, and referring again to FIGURES l-3,the rear vehicle section 11 includes a chassis supported on a wheeltruck 21 by a pivotal mounting arrangement 22 for relative pivotalmovement about its longitudinal axis 23. The pivotal mountingarrangement 22 permits the wheels 25 of the truck 21 to remain incontact with the ground over very uneven terrain. Furthermore, thepivotal mounting arrangement 22 obviates the normal detrimental effectsof longitudinal shock loading in the pivotal connection between thetruck 21 and the chassis 20.

The chassis 20 of the rear vehicle section 11 includes a conventionalpower plant 26 mounted on a generally Y-shaped frame 28. The frame 28includes forwardly extending arms 29 and 30 which cooperate with a pivotshaft to pivotally interconnect the vehicle sections 11 and 13 accordingto the present invention. The shaft 35 defines the axis 12 ofarticulation, of course.

The front vehicle section 13 comprises a chassis 37 mounted on a frontwheel truck 38. The transversely extending axle 39 of the front wheeltruck 38, which mounts front wheels 40, is fixed to the chassis 37 sothat the two chassis 37 and 20 of the vehicle sections 13 and 11,respectively, remain upright during normal, straight ahead travel.

The chassis 37 includes a frame having rearwardly extending arms 46 and47 which cooperate with the shaft 35 to interconnect the vehiclesections 11 and 13 in articulated relationship. A control console 50including a steering wheel 51 is mounted on the frame 45 in front of anoperators seat 52.

The front vehicle section 13 and the rear vehicle section 11 areconventionally interconnected by hydraulic motor means (not shown) toeffect articulation between the vehicle sections. Control of these motormeans is maintained by the operator riding on the front vehicle section13, through the steering wheel 51 suitably connected by a hydraulicsystem (not shown) to the aforementioned hydraulic motor means. Sincesuch a hydraulic system, including the motor means, for articulatingvehicles of this type is conventional and, further, forms no specificpart of the present invention, a more detailed description is consideredunnecessary.

The power plant 26 drives the rear wheels 25 of the vehicle 10 through asuitable drive connection (not shown) in a well-known manner. Inaddition, since the vehicle 10 is a four-wheel drive vehicle, a suitabledrive connection (not shown) is also conventionally provided between thepower plant 26 and the front wheels 40.

As the angular relationship between the front and rear sections 11 and13 of the vehicle 10 is varied to effect turning of the vehicle in awell-known manner, the rearwardly inclined axis 12 of articulation has atendency to cause the front section 13 to tilt toward the inside of theturn. The degree to which the section 13 tends to tilt inwardly isdirectly dependent upon the angle of rearward inclination of the shaft35, as has been pointed out. Furthermore, the greater the angle ofarticulation developed between the front vehicle section 13 and the rearvehicle section 11, the greater the angle at'which the front section 13tends to tilt inwardly of the turn, up to a possible maximum inclinationequal to the degree of rearward inclination of the axis 12. In thepresent instance, a 10 rearward inclination of the axis 12 has beenfound suitable for most working conditions.

Referring to FIGURES 2 and 3, the vehicle 10 embodying features of thepresent invention is shown diagrammtically in about a 3040 turn. Withthis axis 12 tilted rearwardly at 10, the inward tilt of the wheel truck38 (since the truck 38 and chassis 37 are rigidly fixed to each other)tends to be about 3". However, side-loading on the front wheels 40 fromthe outside of the turn tends to tilt the wheel truck 38 in the oppositedirection and the result, according to the present invention, is abalance of forces which leaves the truck 38 in a horizontalrelationship. Accordingly, minimal slippage of the wheels 40 duringoperation is effected.

In addition to the foregoing, the rearward inclination of the axis 12contributes another advantage. When the vehicle 10 is traveling in astraight line on a highway, for example, at relatively high speeds, anyinfluence tending to cause the vehicle to articulate and turn isautomatically counteracted by the imposed compression of the inside tireand a straightening effect is, accordingly, introduced.

Yet another feature of the present invention is embodied in the mountingarrangement 22 which pivotally mounts the chassis 20 on the rear wheeltruck 21 of the rear vehicle section 11, as has been pointed out. Themounting arrangement 22 embodying features of the present invention isconstructed and arranged to virtually eliminate thrust bearing wearnormally encountered with conventional bearing arrangments utilized toprovide such pivotal truck mounting.

Referring to FIGURES 1 and 6, the mounting arrangement 22 comprises aring which carries the axle 106 afiixed thereto. An upwardly extendingear 110 is mounted on the rearmost portion of the ring 105 by welding orthe like and has a bearing passage 111 formed therethrough transverselyof the axle 106. A pin 112 mounted between brackets 115 and 116depending from the chassis 20 of the rear vehicle section 11 extendsthrough the bearing passage 111 and mounts the rear end of the ring 105on the chassis for pivotal movement about the axis 23.

According to the present invention, the mounting arrangement 22 furtherincludes a block 121 mounted on the ring 105 at its forwardmost portionby welding or the like. The block 121 has a segmentally sphericalaperture 122 formed therein which seats a universal ball joint 123mounted on a pin 125. The transversely extending pin 125 is, in turn,supported at its opposite ends in brackets 126 secured to the bottom ofthe chassis 20. The front end of the ring 105 is thus universallysuspended from the chassis 20.

The mounting arrangement 22 permits pivotal movement of the chassis 20about the axis 23 on the rear wheel truck 21 and, in addition, obviatesaxial play between chassis 20 and truck 21 normally encountered when twopin pivot mountings define the axis 22. Accordingly, the forward andrearward thrust forces developed by the driving wheels 25 cannot causedamage through bearing play.

While the embodiment described herein is at present considered to bepreferred, it is understood that various modifications and improvementsmay be made therein, and it is intended to cover in the appended claimall such modifications and improvements as fall within the true spiritand scope of the invention.

What is desired to be claimed and secured by Letters Patent of theUnited States is:

1. In a four-wheel-drive, articulated vehicle including a front framesection supporting a control console including a steering wheel and anoperators seat rearwardly of said control console and a rear framesection supporting a power plant; a rear wheel truck including a pair oflaterally spaced, ground-engaging wheels mounted for rotation about asingle transversely extending axis,

said rear wheel truck being connected to said rear frame section forrelative rocking movement about an axis extending longitudinally of saidrear frame section; a front wheel truck including a pair of laterallyspaced, ground-engaging wheels mounted for rotation about a singletransversely extending axis, said front wheel truck being substantiallyrigidly connected to said front frame section; and means for pivotallyconnecting said front and rear frame sections together for relative movement about an axis of articulation, said axis of articulationintersecting the longitudinal median line of said rear frame section andextending vertically upwardly and horizontally rearwardly from the pointof intersection of said articulation axis and said rear frame sectionlongitudinal median line.

A. HARRY LEVY, Primary Examinerr

1. IN A FOUR-WHEEL-DRIVE, ARTICULATED VEHICLE INCLUDING A FRONT FRAMESECTION SUPPORTING A CONTROL CONSOLE INCLUDING A STEERING WHEEL AND ANOPERATOR''S SEAT REARWARDLY OF SAID CONTROL CONSOLE AND A REAR FRAMESECTION SUPORTING A POWER PLANT; A REAR WHEEL TRUCK INCLUDING A PAIR OFLATERALLY SPACED, GROUND-ENGAGING WHEELS MOUNTED FOR ROTATION ABOUT ASINGLE TRANSVERSELY EXTENDING AXIS, SAID REAR WHEEL TRUCK BEINGCONNECTED TO SAID REAR FRAME SECTION FOR RELATIVE ROCKING MOVEMENT ABOUTAN AXIS EXTENDING LONGITUDINALLY OF SAID REAR FRAME SECTION; A FRONTWHEEL TRUCK INCLUDING A PAIR OF LATERALLY SPACED, GROUND-ENGAGING WHEELSMOUNTED FOR ROTATION ABOUT A